The inspection of packaging of electronic devices such as integrated chip (IC) packaging is well known in the art and is widely used in the electronic industry. ICs, electronic chip or chip packages, in this case of BGA types, are passed in a tray through the inspecting device. The purpose of the inspection is to measure the coplanarity (relative heights), colinearity (alignment) and the height of each individual ball of the solder balls on the BGA of an IC chip. As is known in the prior art these height measurements can be accomplished with laser triangulation methods, interferometry, and other non-contact measurements. However all tend to be complex and difficult to implement in a manufacturing setting.
A number of methods also exist wherein some part of the measuring device touches a portion of the BGA as exemplified by U.S. Pat. No. 5,621,530: "Apparatus and Method for Verifying the Coplanarity of a Ball Grid Array", issued Apr. 15, 1997. That patent describes an apparatus and method that places the IC with a BGA in the so-called live bug mode (i.e. the BGA is facing down) on a transparent surface and directs light through a series of mirrors onto the BGA. The reflected image is then analyzed to determine if the tips of all of the solder balls rest on the transparent surface. The focus information is then used to determine the distance to each solder ball which provides an indication of the coplanarity of the solder balls of the BGA. U.S. Pat. No. 5,465,152: "Method for Coplanarity Inspection of Package or Substrate Warpage for Ball Grid Arrays, Column Arrays and Similar Structures", issued Nov. 7, 1995, provides another apparatus and method for determining coplanarity and warpage. This invention uses index pads which are positioned on the substrate of the BGA. The pads reflect specific incident radiation from which the alignment and heights of the solder ball tops with respect to the surrounding array can be determined. The invention, from the information so obtained, allows one to determine the degree of coplanarity or substrate warpage.
However, the current methods tend to be limited in the parameters each can verify and check. The current methods like the ones described in the two patents mentioned above, for the most part use triangulation methods and specialize in the inspection of one or two parameters (e.g. coplanarity in the examples noted above). Thus, what is needed is a non-invasive easily implemented system which can measure and verify a wide variety of parameters in an expeditious manner. A system which would be able to measure such parameters as height, position, shape, colinearity, and coplanarity all in one simple and straight forward process during the manufacturing process. A method which allows a full three dimensional (3-D) inspection of the chip quality during the manufacturing process.